Servo-brake mechanism



May 27, 1930. o. 1. BADERTSCHER S ERVO BRAKE MECHANI SM Filled sept. 12, 1927 Patented May 27, 1930 UNITED STATES OTTO J. BADEBTSCHEB, F ZURICH, SWITZERLAND sEnvo-Bnaxn MEontANIsu Application mea september 12, 1921. serial No. masso.

This invention relates to mechanism for effecting the braking of vehicles anddeals particularly with servo-brake systems, wherein the brake actuating force comprises a source of pressure, or vacuum pressure, produced by the vehicle engine. A speciic system wherein the present invention is used to great advantage is shown in the coi, ending application for vacuum servo-bra es for motor driven vehicles, Serial No. 152,090,

dated December 2, 1926, of the present applicant.

Where the servo-brake cylinder is mounted at the wheel, it frequently happens that, due

to the size of the wheel, the cylinder must' be mounted apar-lt therefrom and suitable linkage provided to serve as the mechanical connection to the brake.fv The added elements are obviously undesirable and the diioulty of mounting the brake cylinder at the most advantageous location, and maintaining the parts properly serviced, renders itl h1ghly desirable to mount the brake cylinder d1- rectly at the braking mechanism. The pres- 5 ent invention provides a cylinder of suliciently reduced size to enable it to be mounted directly within, or at, the braking mechanism without impairing the effectiveness thereof.

A further object of the invention is-to provide a servo-brake mechanism which multlplies the braking force and provides a desirable amount of lost motion represented by the taking up of the slack on the brake comes effective. l i

A further object of the invention is to provide av servo-brake mechanism which, during its initial movement in taking up the slack in the brake, provides a rapid movement of the brake mechanism, while during final movement represented by the braking action, the `movement is relatively slight and the mechanical advantage, or degree of multiplying the braking force supplied from the engine, relatively great.

The invention will be more apparent as the description proceeds in connection with the accompanying drawings wherein:

Figure 1 is a view in section, taken on line band before the actual braking force be- P 1-1 of Figure 2, showing a preferred form v ofthe invention.

Fi ure 2 is a view, in end elevation, showing t e brake cylinder and associated mechanism of Figure l with the cover plate of Figure 1 removed. y

Figure 3 is a view in section, taken on line 3 3 of Figure l, and looking in the direction of the arrows.

Referring tothe figures described above, a designates a brake rod, or other linkage which is connectedto the brake applying mechanism. b lindicates a conduit which communicates 4with a suitable pressure, or vaccum pressure source, produced by the engine of the vehicle upon `which the braking A device is to be applied. As the description proceeds it will be apparent that the structure embodied in the present invent-ion may be used, with equal facility, in connection with other sources of pressure than that indicated herein, the present' descri tion serving only'to illustrate a specific em odiment of the invention.v

Conduit b is secured toa brake cylinder by 7 5 means of a suitable nipple b', lock nut construction b3 and packing b2. This connection n y should, of course, be Huid tight in order that no loss of pressure may occur. A piston d moves within the cylinder c and is forcedv in one direction by means of a spring e, while, in the other direction, the suction through the conduit b serves to move the iston to actuate the brake mechanism. The side walls d of the piston are provided with a circumferentiall recessed portion d adjacent the head o the piston. Within the recessed portion d2, a packing da is provided and is secured in position by means of an annular ring d, maintained in position by bolts d, It will be quite obvious that the packing d is provided for the purpose of rendering a uid tight connection between the cilinder wall c and the movable iston d.

A caring housin f is connecte on the rear end of the cylin er c and carries a ivot shaft f which pivotally mounts a cam ever f2. This lever moves within a slotted portion f' in the top ofthe cylinder and is connected with the piston d by means of links fand bolt d provided with pivot bearings Z7 which are carried with the links f4. A cam face f5 is formed on tfe inner side of the lever f2 and functions to apply the brake as described hereinafter. y

The shaft a carries a bearing shaft a within a forked shaped portion a2 thereof. Between the forked members a roller a3 is mounted, and on the opposite sides of the forked members, independent rollers a4 are secured to ride on tracks f, carried inside the bearing housing f. It will be apparent from the above description that pivotal movement of the lever f2 to the left causes the roller as to have a rolling engagement with cam face f5, while the rollers a* ride over tracks f", and the rod a is moved axially to the left. During the initial movement of the lever f2, the Aforce applied upon the rod a will be through a relatively great lever arm, represented by the length of the cam face f5. In view of this, the axial movement of the rod a will be rapid during initial movement of the lever f2, but as the roller a rides ,over the cam face f5 the lever arm, through which the braking force is transmitted, becomes progressively shortened and the rate of movement of the rod a decreases while the transmitted force increases. During the initial movement of the mechanism there will be a downward component of force exerted upon the bearing shaft a by the lever f' and this downward force is taken by the rollers as and a. After the playin thebrake mechanism has been taken up, represented by the initial movement of the lever f2, the force transmitted from the lever f2 to the rod a is through a relatively small lever arm and the downward component of force upon the rollers approaches zero. At the point of maximum braking, the cam face f is at right angles with the path of movement of the rollers as and a* and the downward component of force is zero, thus enabling the entire force transmitted from the lever f2 to the rod a to be utilized in braking.

If desired, a suitable protecting cap c is provided to enclose the end of the cylinder c and the mechanism carried thereby. The brake applying mechanism, described above, may be secured to a suitable bracket c2, as shown in Figure 3. The specific form of cap, or manner of securing the structure to the vehicle forms no part of the present invention, and it will be understood that the arrangement of parts and vdesign of the elemen-ts described above may be varied to suit certain conditions as desired.

From the foregoing description it will beA the improved construction, the manufacturing cost thereof is reduced by reason of the smaller sized parts required for its assembly.

Although the invention has been described in connection with a vacuum braking system it is apparent that the force multiplying dcvice may be used in connectibn with other sources of power and the invention is not to be limited save as definedin the appended claims.

I claim as my invention:

1. A servo-brake mechanism for vehicles comprising a driving member, a driven member, a. force transmitting member, means to pivot the force transmitting member at one end to a fixed support, means to connect the driving member pivotally with the other end of the force transmitting member, rollers 4carried by the driven member, tracks upon iwhichcertain of the rollers ride, and a cam face on the force transmitting member to engage another of the rollers, the engagement between the force transmitting member and rollers of the driven member during braking action occurring while the angle between the cam face and the axis of the driven member approaches ninety degrees.

,2. A servo-brake mechanism for vehicles comprising a cylinder, a piston movable therein, means to apply an actuating pressure to Vthe piston, a force transmitting lever, means to pivot the lever in operative relation with the cylinder, means to connect the piston with the leverpivotally, a driven member, rollers carried upon-the end of the driven member, tracks mounted upon the cylinder and upon which certain of the rollers ride, and a cam face on the lever to engage another of the rollers, angle of contact of the cam 'face with the axis of the driven member approaching 90 during braking action.

3. A servo-brake mechanism for vehicles comprising a cylinder, a piston movable therein, means to apply an actuating pressure to the piston, a force transmittlng lever, means to pivot the lever in operative relation with the cylinder, means to connect the piston with the lever pivotally, a driven member, rollers carried upon the end of the driven member, tracks mounted upon the cylinder and upon which certain' of the rollers ride, a slot between the tracks to permit the lever to move therein in its brake applying movement, and a cam face on the lever for engaging another of the rollers, the angle of contact of the face of the cam with the axisof the driven member, varying as the lever is moved.

This specification signed this '7th day of September, A. D. 1927.

OTTO J. BADERTSCHER. 

